PROJECT SUMMARY This R21 application aims to clarify the neurobiological mechanisms by which change occurs during cognitive behavior therapy (CBT) for major depressive disorder (MDD). This hypothesis-driven study will explore the association between the psychological constructs of psychological mindedness (PM) and mindfulness (M) during the time course of CBT for MDD, and its relationship to electrophysiological and behavioral measures of automatic (i.e. stimulus-driven or bottom-up) emotion processing. This objective is motivated by the following rationale: PM and M represent different meta-cognitive processes of self-knowledge deemed critical for emotion regulation (ER) and CBT success. Event-related potentials (ERPs) to salient affective pictures reflect different stages of motivated attention. Using advanced analytic EEG techniques, we have linked these stages to the hierarchical activation of `emotional' brain regions along the occipitotemporal ventral stream, ranging from preconscious stimulus categorization (right secondary visual cortex, right temporoparietal junction) to conscious appraisal (posterior cingulate cortex, ventromedial cortex). Importantly, blunted ERP responses to emotionally-arousing stimuli have been observed in clinical depression, and hypoactivation of right temporoparietal and dorsolateral prefrontal regions normalize after successful antidepressant or electroconvulsive treatment. A dichotic emotion recognition test, which provides an auditory measure of bottom-up emotion processing in form of a left ear (right hemisphere) advantage for recognizing the emotional intonation of speech patterns, has revealed behavioral deficits in MDD patients. Moreover, an increased right ear advantage for verbal stimuli (left hemisphere) is seen in CBT responders. Employing a sample of 60 MDD patients randomly assigned to CBT or nonspecific supportive therapy (placebo), we will obtain psychological, electrophysiological, behavioral and clinical outcome measures of response to 12 weeks of CBT in a pre-post treatment design to determine: (1) when and where in the brain automatic emotion processing is altered by CBT; (2) if changes in emotional responding are moderated or mediated by meta- cognitive processes of self-knowledge; and, (3) if these measures, alone or in combination, have promise as markers of CBT treatment response. Existing ERP and behavioral data for healthy adults (HC) obtained using the same experimental protocols will provide normative (yardstick) data. This study brings together experienced clinical psychologists and psychiatrists doing treatment and research in depression with investigators having expertise in affective neuroscience and electrophysiological studies in MDD. It will provide a critical new step for outlining the affective-cognitive and neurophysiological mechanisms of ER by which change through CBT occurs. Apart from their theoretical relevance, the findings of this project will also aid in developing novel and more targeted interventions and in identifying patients who may benefit most from CBT for unipolar depression.